Wireless computing devices, such as laptop computers, personal digital assistant devices, etc., which communicate with other devices through wireless signals, are becoming increasingly popular. Wireless computing devices are typically mobile and battery-powered. Since the battery capacity is limited, minimizing the energy consumption of a device in order to extend its operation time is an important consideration in the design of battery-operated wireless devices.
A particular component of a wireless device that consumes a significant amount of energy is the network interface card (NIC), which handles the wireless transmission and reception of network communication data. It has been estimated that, on average, about twenty percent of the total energy available to a wireless device is dissipated as a result of using the NIC, or other wireless network interfacing component.
This phenomenon is due to the fact that the NIC of the wireless device must be in a constant “listening” state in order to receive data via the network. As a result, the battery is used to power the device and the NIC even when no data is being received by or transmitted by the device. The NIC also consumes energy while transmitting and receiving messages. However, in typical use, it expends a significant amount of energy in idle mode while waiting for messages.
To improve the battery lifetime of conventional wireless devices, various schemes have been developed and implemented to reduce battery consumption.
One power management scheme often employed by wireless devices entails switching the NIC between different power states that have different energy consumption levels. Those states include a high-power state, in which the NIC is powered up to enable the transmission of network communication data, and a low-power state, in which the network interface card is put in a sleep mode.
When the NIC is in a low-power state, data transmissions can be significantly delayed while the NIC switches to the high-power state and attempts to reconnect to the network. Consequently, the delayed data has to be buffered until the NIC is ready for data communication. A significant amount of delayed network traffic data must be buffered if the interface network card is kept in the low-power state too often or for too long.